TEHRAN -- Iran's chief nuclear negotiator expressed hope for "good and constructive negotiations" as he left Tehran for a meeting in Geneva with world powers on the country's disputed nuclear program.

Iranian media said Said Jalili was asked about the expected presence of a senior U.S. diplomat at the July 19 talks in the Swiss city.

"If they enter [negotiations] with a constructive approach and by avoiding previous mistakes, we can definitely have good and constructive negotiations," Jalili was quoted as saying by the ISNA news agency. "What is important from our view point is with what approach the other side is having a presence in negotiations. The kind of approach is more important than which people would attend the talks."

The United States said on July 16 that it was sending an envoy to Geneva to join nuclear talks with Iran for the first time, to underline to the Islamic Republic and others that Washington wanted a diplomatic solution to the impasse.